Field of the Invention
The invention relates to an internal combustion engine, in particular a diesel engine or an otto-cycle engine, with a fresh-air system in which a charge-air cooler is disposed, an exhaust-gas system, an exhaust-gas turbocharger which has a compressor disposed in the fresh-air system upstream of the charge-air cooler and a turbine disposed in the exhaust-gas system, a first line for a high-pressure exhaust-gas recirculation which, upstream of the turbine of the exhaust-gas turbocharger, branches off from the exhaust-gas system and which has a high-pressure exhaust-gas recirculation valve and which, downstream of the charge-air cooler, opens into the fresh-air system, a second line for a low-pressure exhaust-gas recirculation which, downstream of the turbine of the exhaust-gas turbocharger, branches off from the exhaust-gas system and which has a low-pressure exhaust-gas recirculation valve and which, upstream of the compressor of the exhaust-gas turbocharger, opens into the fresh-air system, and an exhaust-gas flap disposed in the exhaust-gas system downstream of the branch-off of the low-pressure exhaust-gas recirculation line. The invention also relates to a method for operating an internal combustion engine, particularly a diesel engine or an otto-cycle engine, the internal combustion engine having a fresh-air system, an exhaust-gas system, an exhaust-gas turbocharger, which has a compressor disposed in the fresh-air system and a turbine disposed in the exhaust-gas system, wherein recirculated exhaust-gas is diverted from the exhaust-gas system downstream of the turbine of the exhaust-gas turbocharger, via a line for a low-pressure exhaust-gas recirculation, by using a low-pressure exhaust-gas recirculation valve and is fed, upstream of the compressor of the exhaust-gas turbocharger, as a low-pressure exhaust-gas recirculation mass flow into the fresh-air system, wherein an exhaust-gas flap is disposed downstream of the branch-off of the low-pressure exhaust-gas recirculation line.
Japanese Patent Application JP 2004150319 A discloses a diesel combustion engine with a high-pressure exhaust-gas recirculation path (HP-EGR path) and a low-pressure exhaust-gas recirculation path (LP-EGR path), wherein an exhaust-gas flap is provided at the junction where the LP-EGR path branches off from an exhaust-gas line of the diesel combustion engine. The LP-EGR mass flow is extracted downstream of a turbine of an exhaust-gas turbocharger (EGT) on the low pressure side after a device for an exhaust-gas aftertreatment and is fed into the intake air in front of a compressor of the exhaust-gas turbocharger. The low-pressure exhaust-gas recirculation mass flow is cooled down on the way to the compressor inlet. A low-pressure exhaust-gas recirculation valve is provided upstream of the entry of the low-pressure exhaust-gas recirculation mass flow into the fresh air. The low-pressure exhaust-gas recirculation path is used at low and medium rotational speeds and in the middle load range, i.e. when there is a sufficient pressure drop.
Japanese Patent Application JP 2004156572 A discloses a diesel engine which has a high-pressure exhaust-gas recirculation path (HP-EGR path) with a high-pressure exhaust-gas recirculation valve and a low-pressure exhaust-gas recirculation path (LP-EGR path). The low-pressure exhaust-gas recirculation path branches off downstream of a turbine of an exhaust-gas turbocharger (EGT) as well as after an exhaust-gas aftertreatment device and opens into the fresh-air path upstream of a compressor of the exhaust-gas turbocharger. An exhaust-gas flap controls the amount of the low-pressure exhaust-gas recirculation mass flow in accordance with an operating state of the diesel engine.
U.S. Pat. No. 7,013,879 B2 discloses a low-pressure exhaust-gas recirculation path (LP-EGR path) for an internal combustion engine, wherein the LP-EGR path branches off downstream of the turbine of an exhaust-gas turbocharger as well as a particulate filter and, via an EGR cooler as well as a control valve, opens into the fresh-air line directly upstream of the compressor of the exhaust-gas turbocharger.